Receiving responses back

Hello Everyone,

I appreciate helping me with following situation:

In normal processing, I have a requester that talks to a backend. The backend performs some processing and returns response back to requester. At this time, I have setup loadbalancer as shown in [1] below. However, when loadbalancer finishes job, it needs to send back to loadbalancer so that loadbalancer can return response back to requester. How can I accomplish this?

[1]
upstream backend {
server backend1.example.com;
server backend2.example.com;
server 192.0.0.1 backup;
}
server {
location / {
proxy_pass http://backend;
}
}